Idiopathic pulmonary fibrosis (IPF) is a localized fibrotic disorder of unknown etiology. The disease progresses through a stage of chronic alveolitis culminating in tissue damage and fibrosis. Although there are several immunologic abnormalities in these patients, it is unclear if the immune system contributes to the pathogenesis of this disease. We propose to evaluate the ability of alveolar and peripheral blood mononuclear cells to serve as regulators of the immune response and of fibroblast metabolism through studies on the regulation of in vitro antibody synthesis and modulation of fibroblast proliferation and production of protein, collagen and glycosaminoglycan. Investigations on a systemic fibrotic disease, progressive systemic sclerosis, have indicated that altered immunoregulation of antibody synthesis and collagen production may coincide. This study will provide information regarding the immunoregulatory mechanisms involved in a localized fibrotic disease. We hope to gain valuable information regarding the degree to which T lymphcytes and macrophages of the lung and periphery contribute to the disease state in IPF. Comparisons between previous results in systemic fibrotic disease and those obtained in this study on localized fibrosis will provide insight for understanding the fibrotic process and suggesting new sites for therapeutic intervention.